Landfill leachate reverse osmosis concentrate zero discharge resource utilization method

Abstract

The application discloses a kind of landfill leachate reverse osmosis concentrated liquid zero discharge resource methods, including to concentrated liquid into coagulant and carries out coagulation pretreatment, after stirring, the supernatant is filtered to obtain first effluent;Obtain bipolar membrane electrodialysis unit, bipolar membrane electrodialysis unit includes anode chamber, acid chamber, salt chamber, alkali chamber and cathode chamber, anode chamber is directly set with bipolar membrane between acid chamber, acid chamber and salt chamber are directly set with negative film, the salt chamber is set with positive film between alkali chamber, another bipolar membrane is set between alkali chamber and cathode chamber, first effluent passes through salt chamber, under the action of electric field, anion and cation in first effluent respectively pass through negative film and positive film and enter acid chamber and alkali chamber, to realize desalination and obtain second effluent;The pH value of second effluent is adjusted to 2-3, then into UV-Fenton deep oxidation unit, utilize hydroxyl radical to degrade residual dissolved refractory organic matter in second effluent, obtain third effluent.The method can efficiently degrade pollutants, and energy consumption is smaller.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method for zero-discharge resource utilization of landfill leachate reverse osmosis concentrate. Background Technology

[0002] Landfill leachate is a high-concentration organic wastewater produced by municipal solid waste landfills or incineration plants, characterized by its complex composition, high pollutant concentration, and strong toxicity. Currently, membrane treatment technology (especially reverse osmosis) is widely used for the advanced treatment of landfill leachate. However, this process generates a large amount of reverse osmosis concentrate (RO concentrate), which typically exhibits high salt content (conductivity can reach over 40 mS / cm), high ammonia nitrogen, high total organic carbon, and poor biodegradability. Direct discharge of this concentrate would cause serious environmental harm, therefore effective treatment is essential. Existing technologies for treating landfill leachate RO concentrate have significant shortcomings: conventional coagulation and sedimentation processes can only remove some colloidal and suspended organic matter, and have a weak ability to remove dissolved organic matter, resulting in high organic matter concentrations in the treated effluent, which cannot meet the requirements for discharge or reuse; while when high-salt concentrate is treated directly using advanced oxidation processes (such as Fenton and UV-Fenton), the high concentration of inorganic salts will quench hydroxyl radicals, inhibiting oxidation efficiency, resulting in high reagent consumption, high operating costs, and difficulty in consistently meeting the organic matter concentration requirements in the effluent.

[0003] Patent application CN111056682A discloses a method for evaporation, concentration, and segmented crystallization of RO concentrate from landfill leachate. The RO concentrate, after deep softening and organic matter purification pretreatment, is first concentrated using an MVR evaporator, and then crystallized using a forced circulation MVR evaporator. The crystals are washed and dried to obtain industrial-grade sodium chloride. The mother liquor is further cooled and crystallized, and the resulting crystals are washed and dried to obtain industrial-grade potassium chloride. This method uses an MVR evaporator, a forced circulation MVR evaporator, and a cooling crystallizer to perform evaporation, concentration, segmented crystallization, and water washing purification on the pretreated RO concentrate. By controlling the process conditions of evaporation, concentration, and segmented crystallization, industrial salt products of sodium chloride and potassium chloride are obtained in stages. The condensate is reused as circulating cooling water, thus achieving full treatment and resource utilization of the RO concentrate. However, this method consumes a large amount of reagents and has high operating costs.

[0004] On the other hand, while existing combined processes can achieve a certain degree of organic matter removal or desalination, the units lack synergistic coupling. For example, when coagulation and advanced oxidation are simply combined, a high-salt environment persists, consistently inhibiting oxidation efficiency. While electrodialysis can achieve desalination, it fails to effectively link with subsequent deep oxidation units, resulting in lengthy treatment processes and high energy and chemical consumption. Furthermore, existing treatment processes typically focus solely on pollutant mineralization, neglecting the recovery and utilization of acidic, alkaline, or salty byproducts generated during desalination, leading to resource waste. Although processes such as evaporation and crystallization can achieve salt separation, they are energy-intensive, prone to equipment corrosion, and still generate secondary waste such as mixed salts, making it difficult to truly achieve zero emissions. Summary of the Invention

[0005] This invention provides a zero-discharge resource utilization method for landfill leachate reverse osmosis concentrate, which can efficiently degrade pollutants and consumes less energy.

[0006] This invention provides a method for zero-discharge resource utilization of landfill leachate reverse osmosis concentrate, comprising: (1) Add coagulant to the concentrate for coagulation pretreatment, stir and then filter the supernatant to obtain the first effluent; (2) Obtain a bipolar membrane electrodialysis (BMED) unit, wherein the bipolar membrane electrodialysis unit includes an anode chamber, an acid chamber, a salt chamber, an alkali chamber and a cathode chamber, a bipolar membrane is provided between the anode chamber and the acid chamber, an anion membrane is directly provided between the acid chamber and the salt chamber, a cation membrane is provided between the salt chamber and the alkali chamber, and another bipolar membrane is provided between the alkali chamber and the cathode chamber. The first effluent is passed through the salt chamber. Under the action of the electric field, the anions and cations in the first effluent pass through the anion membrane and the cation membrane respectively into the acid chamber and the alkali chamber, thereby achieving desalination to obtain the second effluent. (3) Adjust the pH of the second effluent to 2-3, and then introduce it into the UV-Fenton deep oxidation unit to excite Fe under ultraviolet light. 2+ The catalytic H2O2 generates hydroxyl radicals, which degrade the residual soluble and recalcitrant organic matter in the second effluent to obtain the third effluent.

[0007] This invention adds a coagulant to the concentrate to adsorb and precipitate colloidal and suspended organic matter in the concentrate. This minimizes the contamination and clogging of the membranes by colloidal and suspended organic matter when the first effluent enters the bipolar membrane electrodialysis unit, increasing membrane lifespan. At the same time, it reduces the voltage applied, lowers energy consumption, and reduces costs.

[0008] This invention sets an anion membrane between the salt chamber and the acid chamber, and a cation membrane between the salt chamber and the alkali chamber. Ionization causes the anions and cations in the first effluent from the salt chamber to migrate under the drive of the electric field and combine with H+ in the acid chamber and OH- in the alkali chamber, respectively, to achieve desalination and co-produce acid and alkali, while ammonia nitrogen is oxidized and removed.

[0009] Because the salinity of the second effluent after desalination and ammonia removal is significantly reduced, the hydroxyl radicals in the UV-Fenton deep oxidation unit mainly degrade the residual soluble and recalcitrant organic matter, reducing the consumption and inhibition of reagents by high salt. In fact, even excessively high salt content cannot be eliminated in the UV-Fenton deep oxidation unit, thus achieving efficient removal of organic matter, reducing reagent dosage, and lowering costs.

[0010] Preferably, the coagulant includes FeCl3, polyaluminum chloride, or Al2(SO4)3.

[0011] More preferably, the coagulant further includes PAM (polyacrylamide).

[0012] More preferably, the coagulant is FeCl3 and PAM (polyacrylamide). The iron hydroxide flocs generated by the hydrolysis of FeCl3 provided by this invention adsorb colloidal and suspended organic matter in the concentrate, while PAM promotes floc sedimentation through bridging. After coagulation and sedimentation, colloidal and suspended organic matter in the effluent is effectively removed, and the concentrations of total organic carbon and ammonia nitrogen are significantly reduced.

[0013] More preferably, the dosage of FeCl3 is 1-3.5 g / L, and the dosage of PAM is 40-80 mg / L.

[0014] More preferably, the dosage of FeCl3 is 2 g / L, the dosage of PAM is 60 mg / L, and the stirring reaction time is 20 min.

[0015] Preferably, before the first effluent is introduced into the salt chamber, the pH value of the first effluent is adjusted to 9-10, and then 0.1-0.3 mol / L of Na2CO3 is added.

[0016] This neutralizes and precipitates ions introduced into the coagulant, minimizing the adverse effects of various elements in the coagulant on the membranes. This invention removes Ca from water by adding an appropriate amount of Na₂CO₃. 2+ Mg 2+ Ions are removed to prevent them from forming scale in subsequent bipolar membrane electrodialysis units, which would affect membrane performance; filtration removes the precipitate.

[0017] Preferably, the concentrated solution contains 100-150 mg / L of organic carbon, 20-30 mg / L of ammonia nitrogen, and has a conductivity of 40-50 mS / cm.

[0018] Preferably, the bipolar membrane electrodialysis unit operates at a voltage of 10-60V and a current density of 10-20mA / cm². 2 .

[0019] In a further preferred embodiment, the bipolar membrane electrodialysis device operates at a voltage of 20V and a current density of 15 mA / cm². 2 .

[0020] Preferably, NaSO4 is placed in the anode chamber and the cathode chamber, HCl is placed in the acid chamber, and NaOH is placed in the alkali chamber.

[0021] This invention involves placing corresponding initial solutions in the polar chamber, acid chamber, and alkali chamber. Upon energization, water molecules in the bipolar film interface layer dissociate to generate H₂. + and OH - H + Entering the acid chamber, OH - Upon entering the alkali chamber, the acid combines with the migrating salt ions, achieving simultaneous production of acid and alkali.

[0022] Preferably, the acid and alkali produced by the bipolar membrane electrodialysis unit are recycled for the pH adjustment stage of the coagulation pretreatment unit.

[0023] Preferably, in the UV-Fenton deep oxidation unit, H2O2 and Fe are added to the second effluent. 2+ At the same time, ultraviolet irradiation is carried out.

[0024] More preferably, the dosage of H2O2 is 5-8 g / L, and Fe... 2+ The dosage is 1-3 g / L, and the ultraviolet irradiation reaction time is 1-8 h.

[0025] More preferably, in the UV-Fenton deep oxidation unit, the dosage of H2O2 is 5.5 g / L, and the dosage of Fe is... 2+ The dosage was 2 g / L, and the ultraviolet irradiation reaction time was 2 h.

[0026] Preferably, the acid and alkali produced by the bipolar membrane electrodialysis unit are recycled for the pH adjustment stage of the coagulation pretreatment unit.

[0027] Preferably, the TOC, ammonia nitrogen, conductivity and other indicators of each unit are tested regularly. When the desalination rate of the bipolar membrane electrodialysis unit is lower than 80% or the membrane stack voltage rises by more than 20%, the membrane module is chemically cleaned or the membrane stack is replaced. When the TOC removal rate of the UV-Fenton unit is lower than 70%, the UV lamp is replaced. When the effluent water quality does not meet the reuse standard, the functional components of the corresponding unit are inspected and replaced.

[0028] The process of this invention is convenient to operate and has a clear flow. The modular design of each unit facilitates maintenance and upgrades. The operating status can be monitored by periodically testing the effluent indicators (TOC, ammonia nitrogen, conductivity, etc.) of each unit. When the BMED desalination rate decreases or the UV-Fenton removal rate decreases, maintenance operations such as membrane cleaning and UV lamp replacement can be performed to ensure long-term stable operation of the process.

[0029] This invention achieves significant resource utilization: the bipolar membrane electrodialysis unit co-produces acid and alkali during desalination and ammonia removal, which can be reused in the pH adjustment step of the process (such as Fe removal from coagulation effluent). 3+ Adjusting the pH to 10 and the pH of the UV-Fenton feed water to 3 eliminates the need to purchase acids and alkalis, significantly reducing reagent costs; it also avoids the generation of solid waste such as miscellaneous salts.

[0030] Description of the invention principle: 1. This invention achieves simultaneous removal of salts, ammonia nitrogen, and organic matter from landfill leachate RO concentrate through a three-stage synergistic coupling of coagulation pretreatment, bipolar membrane electrodialysis (BMED), and UV-Fenton deep oxidation. Specifically, the coagulation pretreatment unit utilizes iron hydroxide flocs generated from FeCl3 hydrolysis to adsorb colloidal and suspended organic matter in the concentrate. PAM promotes floc settling through bridging, removing approximately 56% of TOC, effectively reducing the organic matter load and membrane fouling risk in subsequent units. Furthermore, the iron hydroxide flocs generated from FeCl3 hydrolysis, during settling, simultaneously remove a portion of ammonia nitrogen (approximately 37.8%) through adsorption and co-precipitation, further reducing the ammonia nitrogen load in the subsequent BMED unit. (Without this first step, membrane fouling is severe, leading to increased voltage.)

[0031] 2. The bipolar membrane electrodialysis unit adopts a four-membrane stacked structure of bipolar membrane (NaSO4) / / anion membrane cation membrane / bipolar membrane. Under the action of an electric field, water molecules in the bipolar membrane interface layer dissociate into H+. + and OH - They enter the acid chamber (providing H₂) respectively. + ) and alkali chamber (providing OH) - Simultaneously, the cations and anions in the salt chamber migrate under the drive of the electric field and react with H+. + or OH - This process combines salt production with the co-production of acid and alkali. During this process, ammonia nitrogen is oxidized, achieving highly efficient removal (up to 90%). The salinity of the effluent after desalination and ammonia removal is significantly reduced, eliminating the inhibitory effect of high-salinity environments on advanced oxidation processes.

[0032] 3. In the UV-Fenton deep oxidation unit, ultraviolet light excites Fe... 2+ Catalyzing the generation of hydroxyl radicals from H2O2 ( •OH radicals possess extremely strong oxidizing power (oxidation potential up to 2.80 V), capable of non-selectively attacking and mineralizing residual dissolved and recalcitrant organic matter in BMED effluent. Since the BMED unit has already removed over 90% of the salt, the effects of inorganic salts on... • The quenching effect of OH groups allows the UV-Fenton unit to achieve highly efficient oxidation with low reagent dosages, reducing effluent TOC to below 8 mg / L. pH adjustment precipitates Fe ions, forming water that meets the required conditions. Less oxidant is consumed, eliminating the need for excessive salt removal.

[0033] 4. The various units of this invention form a positive feedback synergistic effect: coagulation pretreatment reduces the membrane fouling load of the BMED unit and extends membrane life; after BMED desalination and deammoniation, the inhibition of UV-Fenton by salinity is eliminated, reducing reagent consumption; the acid and alkali byproducts of the BMED unit can be recycled for pH adjustment steps in the process (such as Fe removal after coagulation). 3+ (Alkali adjustment and Fenton pre-acidification) form a closed-loop resource recovery system, eliminating the need to purchase acids and alkalis externally and significantly reducing operating costs. The entire process generates no secondary concentrate, and all pollutants are degraded or converted into recyclable resources, truly achieving zero discharge of landfill leachate RO concentrate.

[0034] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention utilizes a three-stage synergistic treatment process—coagulation pretreatment, bipolar membrane electrodialysis desalination and ammonia removal, and UV-Fenton deep oxidation—to reduce influent TOC from 120 mg / L to 7.8 mg / L, achieving a removal rate of 93.3%; ammonia nitrogen is reduced from 23.8 mg / L to 1.7 mg / L, achieving a removal rate of 90%; and the effluent quality meets stringent discharge and reuse standards. Compared to a single coagulation + UV-Fenton process (effluent TOC of 18.7 mg / L), the TOC removal efficiency is significantly improved.

[0035] 2. This invention truly achieves zero emissions: Throughout the entire process, pollutants are efficiently degraded, salts are converted into recyclable resources (acids and alkalis), no secondary concentrate is generated, and no wastewater is discharged. It achieves full-scale treatment and zero emissions of landfill leachate RO concentrate from the source.

[0036] 3. Low operating cost of the present invention: The present invention removes a large amount of TOC through coagulation pretreatment, which reduces the membrane fouling load of the BMED unit; after BMED desalting and deammoniation, the inhibitory effect of high salt on advanced oxidation is eliminated, which significantly reduces the reagent consumption of the UV-Fenton unit compared with the direct oxidation process; by-product acids and alkalis can be reused, further reducing the overall operating cost. Attached Figure Description

[0037] Figure 1The overall process flow diagram provided for a specific embodiment of the present invention.

[0038] Figure 2 The bar chart shows the influence of different flocculants provided in Examples 1, 4, 5, and 6 of this invention on the coagulation pretreatment effect.

[0039] Figure 3 Line graphs showing the effect of H2O2 dosage on TOC provided in Examples 1, 2, and 3 of this invention.

[0040] Figure 4 The TOC comparison bar charts provided in Embodiment 1 of the present invention and Comparative Examples 1, 2, and 3 are examples of TOC comparison bar charts.

[0041] Figure 5 This is a TOC comparison curve provided in Example 1 of the present invention.

[0042] Figure 6 The graph showing the change of BMED voltage over time is provided in Comparative Example 2, which is Embodiment 1 of the present invention.

[0043] Figure 7 This is a comparison photograph of the cathode film (a) and anode film (b) after BMED operation, provided in Example 2 of Embodiment 1 of the present invention. Detailed Implementation

[0044] The specific embodiments of the present invention realize a zero-emission treatment process for landfill leachate desalination and deammoniation and simultaneous degradation of organic matter, including a coagulation pretreatment unit, a bipolar membrane electrodialysis unit and a UV-Fenton deep oxidation unit connected in sequence.

[0045] The coagulation pretreatment unit includes a stirred reaction tank, which is equipped with a stirring device (a fast stirring paddle and a slow stirring paddle can share the same device and the speed can be adjusted by frequency conversion control). The bottom of the tank is equipped with a sludge discharge port; the upper part of the side wall of the tank is equipped with a water inlet and a water outlet; the water outlet of the stirred reaction tank is connected to the subsequent pH adjustment tank through a pipeline.

[0046] The bipolar membrane electrodialysis unit includes a bipolar membrane electrodialysis device. The electrodialysis unit adopts a four-membrane stacked structure of bipolar membrane / anion membrane / cation membrane / bipolar membrane, and is equipped with an electrode system (anode and cathode) and a DC power supply. The device is provided with an inlet, an outlet, an acid outlet and an alkali outlet. The acid outlet and the alkali outlet are connected to the coagulation effluent pH adjustment tank and the UV-Fenton influent pH adjustment tank through pipelines.

[0047] The UV-Fenton deep oxidation unit includes a photoreactor, which is equipped with a UV lamp (12W), an aeration device at the bottom of the reactor, and an inlet, a dosing port, and an outlet on the side wall of the reactor.

[0048] As an optional solution, an intermediate equalization tank is provided between the coagulation pretreatment unit and the bipolar membrane electrodialysis unit to adjust the pH of the coagulated effluent and remove residual Fe. 3+ Ca 2+ Mg 2+ Ions; a two-stage intermediate conditioning tank is provided between the bipolar membrane electrodialysis unit and the UV-Fenton deep oxidation unit to adjust the pH of the BMED effluent to acidic conditions. Both intermediate conditioning tanks are equipped with stirring devices and online pH monitors.

[0049] Furthermore, the process system is also equipped with an automatic control system, which is used to monitor the effluent conductivity, pH value, TOC and ammonia nitrogen concentration of each unit in real time, and automatically adjust the dosage of the dosing pump, motor speed and ultraviolet lamp power according to the monitoring data.

[0050] This invention utilizes the aforementioned process to achieve zero-emission treatment of landfill leachate, simultaneously desalinizing and deammonerating it with the degradation of organic matter. Specifically, it includes the following steps: (1) Coagulation pretreatment: The RO concentrate of landfill leachate is fed into the stirred reaction tank of the coagulation pretreatment unit. First, FeCl3 coagulant is added and the mixture is stirred rapidly at 180 r / min for 10 min. Then, PAM is added and the mixture is stirred slowly at 60 r / min for 10 min. Finally, the mixture is allowed to settle for 1 h. The supernatant is then filtered to remove colloidal and suspended organic matter. The dosage of FeCl3 is 1-3.5 g / L and the dosage of PAM is 40-80 mg / L. Preferably, the dosage of FeCl3 is 2 g / L and the dosage of PAM is 60 mg / L.

[0051] (2) First-level intermediate adjustment and softening: The effluent from the coagulation pretreatment unit is fed into a primary intermediate equalization tank to adjust the pH to 9 (preferably using alkali byproducts from the bipolar membrane electrodialysis unit), so that the residual Fe... 3+ The ions are converted into ferric hydroxide precipitate for removal; simultaneously, sodium carbonate is added at a ratio of 0.2 mol / L to remove Ca from the water. 2+ Mg 2+ Ions are removed to prevent them from forming scale in the subsequent bipolar membrane electrodialysis unit and affecting membrane performance; after filtration to remove the precipitate, the filtrate is passed into the bipolar membrane electrodialysis unit.

[0052] (3) Bipolar membrane electrodialysis for desalination and deammoniation: The bipolar membrane electrodialysis unit operates at a voltage of 10-60 V and a current density of 10-20 mA / cm². 2Under the action of an electric field, desalination and deammoniation are carried out. After treatment, the conductivity of the effluent is reduced to below 5 mS / cm and the ammonia nitrogen concentration is reduced to 2.2 mg / L. At the same time, acid and alkali are produced in the desalination and deammoniation process, which are collected from the acid outlet and alkali outlet respectively and reused in the coagulation effluent pH adjustment tank and the UV-Fenton influent pH adjustment tank.

[0053] (4) Secondary intermediate adjustment and UV-Fenton deep oxidation: The effluent from the bipolar membrane electrodialysis unit is fed into a secondary intermediate conditioning tank to adjust the pH to 3 (preferably using the acid produced as a byproduct of the bipolar membrane electrodialysis unit) to meet the optimal acidic conditions for the UV-Fenton reaction. Then, the effluent is fed into the UV-Fenton deep oxidation unit, where FeSO4 is added (at a dosage of 2 g / L), and H2O2 is added at a ratio of 0.8 g / L per 100 mL of reaction solution. The mixture is then irradiated with a 12W UV lamp for 2 hours to degrade residual soluble and recalcitrant organic matter, reducing the total organic carbon in the effluent to below 8 mg / L, thus achieving zero discharge and reuse of the concentrate.

[0054] (5) System monitoring and maintenance steps: Regularly test indicators such as TOC, ammonia nitrogen, and conductivity of each unit. When the desalination rate of the bipolar membrane electrodialysis unit is lower than 80% or the membrane stack voltage rises by more than 20%, perform chemical cleaning of the membrane module or replace the membrane stack. When the TOC removal rate of the UV-Fenton unit is lower than 70% or the UV lamp intensity decays to less than 80% of the initial value, replace the UV lamp tube. When the effluent water quality does not meet the reuse standards, conduct a comprehensive inspection and replace the functional components of the corresponding unit.

[0055] 3. Optimal range of key parameters As a preferred embodiment of the present invention, in the coagulation pretreatment unit, the dosage of FeCl3 is 1-3.5 g / L, the dosage of PAM is 40-80 mg / L, the rapid stirring speed is 150-200 r / min, and the slow stirring speed is 50-70 r / min.

[0056] As a preferred embodiment of the present invention, in the primary intermediate conditioning tank, the pH is adjusted to 9-10, and the dosage of Na2CO3 is 0.15-0.25 mol / L.

[0057] As a preferred embodiment of the present invention, the bipolar membrane electrodialysis unit operates at a voltage of 10-60 V and a current density of 10-20 mA / cm². 2 The treated effluent has a conductivity of less than 5 mS / cm and an ammonia nitrogen concentration of less than 3 mg / L.

[0058] As a preferred embodiment of the present invention, the pH in the secondary intermediate conditioning tank is adjusted to 2.5-4.0; preferably, the pH is adjusted to 3.0.

[0059] As a preferred embodiment of the present invention, in the UV-Fenton deep oxidation unit, H2O2 is added at a ratio of 0.4-1.2 g / L per 100 mL of reaction solution, the amount of FeSO4 added is 1-3 g / L, the power of the ultraviolet lamp is 10-15 W, and the reaction time is 90-150 min.

[0060] 4. Methods for recycling by-product acids and alkalis The acid and alkali produced by the bipolar membrane electrodialysis unit in this invention can be reused in the following manner: (1) The by-product alkaline solution is recycled to the primary intermediate equalization tank to adjust the pH of the coagulated effluent to 9, so as to remove Fe by precipitation. 3 + Ca 2+ Mg 2+ ion; (2) The by-product acid solution is recycled to the secondary intermediate conditioning tank to adjust the pH of the BMED effluent to 3 in order to meet the optimal acidic conditions for the UV-Fenton reaction. All the following examples and comparative examples use RO concentrate leachate from a waste incineration plant as the raw water, with the following water quality characteristics: TOC = 120 mg / L, NH3-N = 23.8 mg / L, conductivity = 48.2 mS / cm (pH = 7.2). Each example fully includes five steps: coagulation pretreatment, primary intermediate conditioning (softening), BMED treatment, secondary intermediate conditioning, and UV-Fenton oxidation, and the final effluent water quality is given.

[0061] Example 1 Influent water quality: TOC=120 mg / L, NH3-N=23.8 mg / L, conductivity=48.2 mS / cm.

[0062] Coagulation pretreatment: FeCl3 (2 g / L) was added to the concentrate, and the mixture was stirred rapidly at 180 r / min for 10 min. Then, PAM (60 mg / L) was added, and the mixture was stirred slowly at 60 r / min for 10 min. After settling for 1 h, the supernatant was collected and filtered. The effluent TOC was 52.2 mg / L, and NH3-N was 14.8 mg / L.

[0063] First-stage intermediate adjustment: Adjust the pH of the coagulated effluent to 9, add Na2CO3 with a concentration of 0.2 mol / L in the solution, stir, and then filter to remove the precipitate.

[0064] BMED Treatment: The conditioned effluent is fed into a bipolar membrane electrodialysis unit, which includes an anode chamber, an acid chamber, a salt chamber, an alkali chamber, and a cathode chamber. A bipolar membrane is placed between the anode chamber and the acid chamber; an anion membrane is placed directly between the acid chamber and the salt chamber; a cation membrane is placed between the salt chamber and the alkali chamber; and another bipolar membrane is placed between the alkali chamber and the cathode chamber. The first effluent is passed through the salt chamber. Under the action of an electric field, the anions and cations in the first effluent pass through the anion membrane and the cation membrane respectively into the acid chamber and the alkali chamber, thereby achieving desalination to obtain the second effluent. The electrode solution is 0.7 mol / L Na2SO4, the initial solution in the acid chamber is 0.05 mol / L hydrochloric acid, and the initial solution in the alkali chamber is 0.05 mol / L sodium hydroxide. The current density is controlled at 15 mA / cm². 2 (Initial voltage approximately 20 V, termination voltage approximately 48 V), treatment for 4 hours. Effluent conductivity = 4 mS / cm, NH3-N = 2.2 mg / L, TOC = 44.2 mg / L. Acids and alkalis were also produced as byproducts.

[0065] Secondary intermediate adjustment: Adjust the pH of the BMED effluent to 3 (using by-product acid).

[0066] UV-Fenton oxidation: Take 100 mL of adjusted effluent, add 0.2 g FeSO4, and continuously add H2O2 at a rate of 0.8 g / h. React for 2 h under 12 W UV lamp irradiation.

[0067] The final effluent has a TOC of 7.8 mg / L and an NH3-N concentration of 1.7 mg / L, both meeting the reuse standards. There is no secondary concentrate discharge, and the by-product acids and alkalis are recycled into the primary and secondary equalization tanks, achieving zero discharge and resource utilization.

[0068] Example 2 Influent water quality: TOC=120 mg / L, NH3-N=23.8 mg / L, conductivity=48.2 mS / cm.

[0069] Coagulation pretreatment: FeCl3 (2 g / L) was added to the concentrate, and the mixture was stirred rapidly at 180 r / min for 10 min. Then, PAM (60 mg / L) was added, and the mixture was stirred slowly at 60 r / min for 10 min. After settling for 1 h, the supernatant was collected and filtered. The effluent TOC was 52.2 mg / L, and NH3-N was 14.8 mg / L.

[0070] First-stage intermediate adjustment: Adjust the pH of the coagulated effluent to 9, add Na2CO3 with a concentration of 0.2 mol / L in the solution, stir, and then filter to remove the precipitate.

[0071] BMED Treatment: The conditioned effluent is fed into a bipolar membrane electrodialysis unit. This unit includes an anode chamber, an acid chamber, a salt chamber, an alkali chamber, and a cathode chamber. A bipolar membrane is positioned between the anode and acid chambers; an anion membrane is directly positioned between the acid and salt chambers; a cation membrane is positioned between the salt and alkali chambers; and another bipolar membrane is positioned between the alkali and cathode chambers. The first effluent is passed through the salt chamber. Under the influence of an electric field, the anions and cations in the first effluent pass through the anion and cation membranes respectively into the acid and alkali chambers, thus achieving desalination to obtain the second effluent. The electrode solution is 0.7 mol / L Na₂SO₄, the initial solution in the acid chamber is 0.05 mol / L hydrochloric acid, and the initial solution in the alkali chamber is 0.05 mol / L sodium hydroxide. The current density is controlled at 15 mA / cm². 2 (Initial voltage approximately 20 V, termination voltage approximately 48 V), treatment for 4 hours. Effluent conductivity = 4 mS / cm, NH3-N = 2.2 mg / L, TOC = 44.2 mg / L. Acids and alkalis were also produced as byproducts.

[0072] Secondary intermediate adjustment: Adjust the pH of the BMED effluent to 3 (using by-product acid).

[0073] UV-Fenton oxidation: Take 100 mL of adjusted effluent, add 0.2 g FeSO4, and continuously add H2O2 at a rate of 0.4 g / h. React for 2 h under 12 W UV lamp irradiation.

[0074] The final effluent had a TOC of 12.6 mg / L and an NH3-N concentration of 2.1 mg / L.

[0075] Example 3 Influent water quality: TOC=120 mg / L, NH3-N=23.8 mg / L, conductivity=48.2 mS / cm.

[0076] Coagulation pretreatment: FeCl3 (2 g / L) was added to the concentrate, and the mixture was stirred rapidly at 180 r / min for 10 min. Then, PAM (60 mg / L) was added, and the mixture was stirred slowly at 60 r / min for 10 min. After settling for 1 h, the supernatant was collected and filtered. The effluent TOC was 52.2 mg / L, and NH3-N was 14.8 mg / L.

[0077] First-stage intermediate adjustment: Adjust the pH of the coagulated effluent to 9, add Na2CO3 with a concentration of 0.2 mol / L in the solution, stir, and then filter to remove the precipitate.

[0078] BMED Treatment: The conditioned effluent is fed into a bipolar membrane electrodialysis unit. This unit includes an anode chamber, an acid chamber, a salt chamber, an alkali chamber, and a cathode chamber. A bipolar membrane is positioned between the anode and acid chambers; an anion membrane is directly positioned between the acid and salt chambers; a cation membrane is positioned between the salt and alkali chambers; and another bipolar membrane is positioned between the alkali and cathode chambers. The first effluent is passed through the salt chamber. Under the influence of an electric field, the anions and cations in the first effluent pass through the anion and cation membranes respectively into the acid and alkali chambers, thus achieving desalination to obtain the second effluent. The electrode solution is 0.7 mol / L Na₂SO₄, the initial solution in the acid chamber is 0.05 mol / L hydrochloric acid, and the initial solution in the alkali chamber is 0.05 mol / L sodium hydroxide. The current density is controlled at 15 mA / cm². 2 (Initial voltage approximately 10 V, termination voltage approximately 48 V), treatment for 4 hours. Effluent conductivity = 4 mS / cm, NH3-N = 2.2 mg / L, TOC = 44.2 mg / L. Acids and alkalis were also produced as byproducts.

[0079] Secondary intermediate adjustment: Adjust the pH of the BMED effluent to 3 (using by-product acid).

[0080] UV-Fenton oxidation: Take 100 mL of adjusted effluent, add 0.2 g FeSO4, and continuously add H2O2 at a rate of 1.2 g / h. React for 2 h under 12 W UV lamp irradiation.

[0081] The final effluent had a TOC of 7.6 mg / L and an NH3-N concentration of 1.8 mg / L.

[0082] Example 4: FeCl3 coagulation only, without PAM Influent water quality: TOC=120 mg / L, NH3-N=23.75 mg / L, conductivity=48.2 mS / cm.

[0083] Coagulation pretreatment: FeCl3 (2 g / L) was added to the concentrate, and the mixture was stirred rapidly at 180 r / min for 10 min. Then, without adding PAM, the mixture was stirred slowly at 60 r / min for 10 min. After settling for 1 h, the supernatant was collected and filtered. The effluent TOC was 67.55 mg / L, and NH3-N was 16.7 mg / L.

[0084] First-stage intermediate adjustment: Adjust the pH of the coagulated effluent to 9, add Na2CO3 with a concentration of 0.2 mol / L in the solution, stir, and then filter to remove the precipitate.

[0085] BMED Treatment: The conditioned effluent is fed into a bipolar membrane electrodialysis unit. This unit includes an anode chamber, an acid chamber, a salt chamber, an alkali chamber, and a cathode chamber. A bipolar membrane is positioned between the anode and acid chambers; an anion membrane is directly positioned between the acid and salt chambers; a cation membrane is positioned between the salt and alkali chambers; and another bipolar membrane is positioned between the alkali and cathode chambers. The first effluent is passed through the salt chamber. Under the influence of an electric field, the anions and cations in the first effluent pass through the anion and cation membranes respectively into the acid and alkali chambers, thus achieving desalination to obtain the second effluent. The electrode solution is 0.7 mol / L Na₂SO₄, the initial solution in the acid chamber is 0.05 mol / L hydrochloric acid, and the initial solution in the alkali chamber is 0.05 mol / L sodium hydroxide. The current density is controlled at 15 mA / cm². 2 (Initial voltage approximately 20 V, termination voltage approximately 48 V), treatment for 4 hours. Effluent conductivity = 8 mS / cm, NH3-N = 2.6 mg / L, TOC = 53.36 mg / L. Acids and alkalis were also produced as byproducts.

[0086] Secondary intermediate adjustment: Adjust the pH of the BMED effluent to 3 (using by-product acid).

[0087] UV-Fenton oxidation: Take 100 mL of adjusted effluent, add 0.2 g FeSO4, and continuously add H2O2 at a rate of 0.8 g / h. React for 2 h under 12 W UV lamp irradiation.

[0088] The final effluent had a TOC of 13.9 mg / L and an NH3-N concentration of 2.1 mg / L.

[0089] Example 5: Using polyaluminum chloride (PAC) + PAM Influent water quality: TOC=120 mg / L, NH3-N=23.8 mg / L, conductivity=48.2 mS / cm.

[0090] Coagulation pretreatment: PAC (2 g / L) was added to the concentrate, and the mixture was stirred rapidly at 180 r / min for 10 min. Then PAM (60 mg / L) was added, and the mixture was stirred slowly at 60 r / min for 10 min. After settling for 1 h, the supernatant was collected and filtered. The effluent TOC was 78.6 mg / L, and NH3-N was 18.9 mg / L.

[0091] First-stage intermediate adjustment: Adjust the pH of the coagulated effluent to 9, add Na2CO3 with a concentration of 0.2 mol / L in the solution, stir, and then filter to remove the precipitate.

[0092] BMED Treatment: The conditioned effluent is fed into a bipolar membrane electrodialysis unit. This unit includes an anode chamber, an acid chamber, a salt chamber, an alkali chamber, and a cathode chamber. A bipolar membrane is positioned between the anode and acid chambers; an anion membrane is directly positioned between the acid and salt chambers; a cation membrane is positioned between the salt and alkali chambers; and another bipolar membrane is positioned between the alkali and cathode chambers. The first effluent is passed through the salt chamber. Under the influence of an electric field, the anions and cations in the first effluent pass through the anion and cation membranes respectively into the acid and alkali chambers, thus achieving desalination to obtain the second effluent. The electrode solution is 0.7 mol / L Na₂SO₄, the initial solution in the acid chamber is 0.05 mol / L hydrochloric acid, and the initial solution in the alkali chamber is 0.05 mol / L sodium hydroxide. The current density is controlled at 15 mA / cm². 2 (Initial voltage approximately 20 V, termination voltage approximately 48 V), treatment for 4 hours. Effluent conductivity = 11 mS / cm, NH3-N = 3.3 mg / L, TOC = 65.8 mg / L. Acids and alkalis were also produced as byproducts.

[0093] Secondary intermediate adjustment: Adjust the pH of the BMED effluent to 3 (using by-product acid).

[0094] UV-Fenton oxidation: Take 100 mL of adjusted effluent, add 0.2 g FeSO4, and continuously add H2O2 at a rate of 0.8 g / h. React for 2 h under 12 W UV lamp irradiation.

[0095] The final effluent had a TOC of 17.5 mg / L and an NH3-N concentration of 2.4 mg / L.

[0096] Example 6: Al2(SO4)3+PAM was used instead Influent water quality: TOC=120 mg / L, NH3-N=23.8 mg / L, conductivity=48.2 mS / cm.

[0097] Coagulation pretreatment: Al2(SO4)3 (2 g / L) was added to the concentrate, and the mixture was stirred rapidly at 180 r / min for 10 min. Then, PAM (60 mg / L) was added, and the mixture was stirred slowly at 60 r / min for 10 min. After settling for 1 h, the supernatant was collected and filtered. The effluent TOC was 58.9 mg / L, and NH3-N was 15.7 mg / L.

[0098] First-stage intermediate adjustment: Adjust the pH of the coagulated effluent to 9, add Na2CO3 with a concentration of 0.2 mol / L in the solution, stir, and then filter to remove the precipitate.

[0099] BMED Treatment: The conditioned effluent is fed into a bipolar membrane electrodialysis unit. This unit includes an anode chamber, an acid chamber, a salt chamber, an alkali chamber, and a cathode chamber. A bipolar membrane is positioned between the anode and acid chambers; an anion membrane is directly positioned between the acid and salt chambers; a cation membrane is positioned between the salt and alkali chambers; and another bipolar membrane is positioned between the alkali and cathode chambers. The first effluent is passed through the salt chamber. Under the influence of an electric field, the anions and cations in the first effluent pass through the anion and cation membranes respectively into the acid and alkali chambers, thus achieving desalination to obtain the second effluent. The electrode solution is 0.7 mol / L Na₂SO₄, the initial solution in the acid chamber is 0.05 mol / L hydrochloric acid, and the initial solution in the alkali chamber is 0.05 mol / L sodium hydroxide. The current density is controlled at 15 mA / cm². 2 (Initial voltage approximately 20 V, termination voltage approximately 48 V), treatment for 4 hours. Effluent conductivity = 5 mS / cm, NH3-N = 2.4 mg / L, TOC = 51.7 mg / L. Acids and alkalis were also produced as byproducts.

[0100] Secondary intermediate adjustment: Adjust the pH of the BMED effluent to 3 (using by-product acid).

[0101] UV-Fenton oxidation: Take 100 mL of adjusted effluent, add 0.2 g FeSO4, and continuously add H2O2 at a rate of 0.8 g / h. React for 2 h under 12 W UV lamp irradiation.

[0102] The final effluent had a TOC of 11.4 mg / L and an NH3-N concentration of 2.4 mg / L.

[0103] Comparative Example 1: Desalting and Deammoniation without BMED Influent water quality: TOC=120 mg / L, NH3-N=23.8 mg / L, conductivity=48.2 mS / cm.

[0104] Coagulation pretreatment: FeCl3 (2 g / L) was added to the concentrate, and the mixture was stirred rapidly at 180 r / min for 10 min. Then, PAM (60 mg / L) was added, and the mixture was stirred slowly at 60 r / min for 10 min. After settling for 1 h, the supernatant was collected and filtered. The effluent had a TOC of 52.2 mg / L, NH3-N of 14.8 mg / L, and a pH of approximately 3.

[0105] UV-Fenton oxidation: Take 100 mL of coagulated effluent, add 0.2 g FeSO4, and then continuously add H2O2 at a rate of 0.8 g / h. React under 12 W UV lamp irradiation for 2 h.

[0106] The final effluent had a TOC of 18.7 mg / L and NH3-N of 13.9 mg / L. The high TOC and substandard ammonia nitrogen levels indicate that the lack of BMED desalination and ammonia removal, coupled with the high-salt environment (conductivity still 48 mS / cm) and residual ammonia nitrogen (22 mg / L), severely inhibited Fenton oxidation efficiency, and the ammonia nitrogen was not completely removed. Therefore, BMED desalination and ammonia removal is a crucial step in achieving the required standards.

[0107] Comparative Example 2: No coagulation, only BMED + UV-Fenton Influent water quality: TOC=120 mg / L, NH3-N=23.8 mg / L, conductivity=48.2 mS / cm.

[0108] First-stage intermediate adjustment: The coagulation pretreatment step is omitted. The pH of the raw water is directly adjusted to 9, and Na2CO3 with a concentration of 0.2 mol / L in the solution is added. After stirring, the solution is filtered to remove the precipitate.

[0109] BMED treatment: The conditioned effluent is passed into a bipolar membrane electrodialysis unit, with the current density controlled at 15 mA / cm². 2 (Initial voltage approximately 30 V, termination voltage approximately 60 V), treatment for 4 hours. Effluent conductivity = 8 mS / cm, NH3-N = 3.2 mg / L, TOC = 98.6 mg / L. Acids and alkalis were also produced as byproducts.

[0110] Secondary intermediate adjustment: Adjust the pH of the BMED effluent to 3 (using by-product acid).

[0111] UV-Fenton oxidation: Take 100 mL of adjusted effluent, add 0.2 g FeSO4, and continuously add H2O2 at a rate of 0.8 g / h. React for 2 h under 12 W UV lamp irradiation.

[0112] The final effluent had a TOC of 25.2 mg / L and an NH3-N of 2.7 mg / L. The TOC did not meet the standard, indicating that omitting coagulation pretreatment would lead to a large amount of organic matter entering subsequent units, and UV-Fenton alone could not completely mineralize it.

[0113] Comparative Example 3: No UV lamp, dark Fenton Influent water quality: TOC=120 mg / L, NH3-N=23.8 mg / L, conductivity=48.2 mS / cm.

[0114] Coagulation pretreatment: FeCl3 (2 g / L) was added to the concentrate, and the mixture was stirred rapidly at 180 r / min for 10 min. Then, PAM (60 mg / L) was added, and the mixture was stirred slowly at 60 r / min for 10 min. After settling for 1 h, the supernatant was collected and filtered. The effluent TOC was 52.2 mg / L, and NH3-N was 14.8 mg / L.

[0115] First-stage intermediate adjustment: Adjust the pH of the coagulated effluent to 9, add Na2CO3 with a concentration of 0.2 mol / L in the solution, stir, and then filter to remove the precipitate.

[0116] BMED treatment: The conditioned effluent is passed into a bipolar membrane electrodialysis unit, with the current density controlled at 15 mA / cm². 2 (Initial voltage approximately 20 V, termination voltage approximately 48 V), treatment for 4 hours. Effluent conductivity = 5 mS / cm, NH3-N = 2.9 mg / L, TOC = 44.2 mg / L. Acids and alkalis were also produced as byproducts.

[0117] Secondary intermediate adjustment: Adjust the pH of the BMED effluent to 3 (using by-product acid).

[0118] UV-Fenton oxidation: Take 100 mL of adjusted effluent, add 0.2 g FeSO4, and then continuously add H2O2 at a rate of 0.8 g / h. React for 2 h without turning on the UV lamp.

[0119] The final effluent TOC was 28.6 mg / L and NH3-N was 2.4 mg / L. The TOC did not meet the standard, indicating that ultraviolet light has a significant synergistic enhancing effect on the Fenton reaction, and the oxidation efficiency decreased significantly in the absence of ultraviolet light.

[0120] like Figure 2 As shown in the comparative experiment of flocculants, the TOC after treatment with FeCl3 and PAM was 44.2 mg / L, lower than that of Al2(SO4)3+PAM (58.9 mg / L) and PAC+PAM (65.8 mg / L); the TOC of FeCl3 alone (without PAM) was 67.55 mg / L, the highest among all combinations. This indicates that PAM has a significant synergistic effect on the flocculation effect of ferric chloride. This is because the positively charged colloids formed by the hydrolysis of ferric salts can effectively neutralize organic matter, and then the bridging effect of PAM promotes the rapid growth and sedimentation of flocs. In contrast, Al2(SO4)3 and PAC have weaker organic matter removal capabilities under the current water quality conditions, and the effect of PAC+PAM is lower than that of Al2(SO4)3+PAM. In summary, under the conditions of this experiment, the flocculation effect of ferric chloride + PAM is better than that of other combinations.

[0121] like Figure 3As shown, under three H2O2 addition rates, the TOC concentration in the UV-Fenton deep oxidation unit continuously decreased with increasing reaction time, and the rate of decrease gradually slowed down. Specifically, at an addition rate of 0.4 g / h, the TOC residue after 2 h of reaction was approximately 12.6 mg / L, significantly lower than the other two groups. The removal curves for addition rates of 0.8 g / h and 1.2 g / h were quite similar. Although the removal rate of the 1.2 g / h group was slightly faster in the initial stage of the reaction, the final TOC residue was almost the same as that of the 0.8 g / h group (0.2 mg / L). Considering both the cost of H2O2 reagents and operational economics, an addition rate of 0.8 g / h was more suitable, as this condition ensures efficient removal of organic matter while avoiding unnecessary reagent waste.

[0122] like Figure 4 As shown, the complete process yields the lowest effluent TOC at 7.8 mg / L. When the bipolar membrane electrodialysis unit is omitted, the effluent TOC rises to 18.7 mg / L, indicating that the high-salt environment without desalination significantly inhibits the oxidation efficiency of UV-Fenton. When the coagulation pretreatment unit is omitted, the effluent TOC is 25.2 mg / L, indicating that failure to remove colloidal and suspended organic matter leads to membrane fouling and increased subsequent oxidation load. When UV irradiation is omitted, the effluent TOC is the highest, reaching 28.6 mg / L, confirming the significant synergistic effect of UV light on the Fenton reaction. These results indicate that coagulation pretreatment, bipolar membrane electrodialysis desalination and ammonia removal, and UV-Fenton deep oxidation are all indispensable. The complete process can achieve the lowest residual TOC (7.8 mg / L), meeting stringent reuse and discharge standards.

[0123] like Figure 5 As shown, the initial TOC of the complete process was 44.2 mg / L, while that of the process without bipolar membrane was 52.2 mg / L. With increasing reaction time, both curves showed a trend of initial rapid decrease followed by gradual slowdown and eventual stabilization. Notably, even with further extended reaction time, the TOC concentration in Comparative Example 1 could not be reduced to the level of Example 1. This phenomenon indicates that the effluent from Comparative Example 1 contained some persistent organic matter that was difficult to mineralize with hydroxyl radicals. This was because the effluent did not undergo bipolar membrane electrodialysis desalination; the high-salt environment quenched some hydroxyl radicals, preventing the complete degradation of organic matter with poor salt tolerance. In contrast, Example 1 eliminated salinity inhibition through pre-desalination, allowing the UV-Fenton unit to oxidize the organic matter to a lower residual level. Therefore, the "non-degradable residue" present in Comparative Example 1 cannot be compensated for by time alone; pre-desalination with the BMED unit is necessary to achieve deep purification.

[0124] like Figure 6As shown, the voltage curves of the flocculated effluent and the 3wt% NaCl solution provided in Example 1 are basically the same, and both remain at a low level in the early stage of operation. However, the voltage of the unflocculated raw water provided in Comparative Example 2 rises rapidly in the early stage of operation and remains at a high level, indicating that the residual organic matter and suspended solids in the raw water increase the membrane stack resistance, resulting in increased operating energy consumption.

[0125] In this specific embodiment of the invention, a 3 wt% NaCl solution was selected as a control to remove the effects of organic matter and suspended solids under the same high-salt background. The salinity of this solution is similar to that of the RO concentrate but does not contain organic matter. If the BMED operating voltage is low and the membrane fouling is mild, while the unflocculated raw water has a high voltage and severe membrane fouling, it proves that the residual organic matter and suspended solids in the raw water are the root cause of the increased membrane resistance and aggravated fouling. The flocculated effluent and the 3 wt% NaCl solution showed basically the same operating performance, further verifying that flocculation pretreatment can effectively eliminate the above-mentioned adverse effects and is a key pre-treatment step to ensure the long-term stable operation of the BMED.

[0126] Figure 7 a and Figure 7 b in the image shows a comparison photograph of the cathode and anode membranes after BMED operation: Comparative Example 2 provides the non-flocculation conditions ( Figure 7 The right figure of 'a' in the middle. Figure 7 In the right figure of b in Example 1, a significant layer of contaminant deposits adheres to the membrane surface, covering it evenly and making it difficult to rinse. However, after flocculation pretreatment in Example 1, the membrane surface fouling is significantly reduced. The above results indicate that flocculation pretreatment not only reduces the contaminant load of the BMED but also effectively alleviates membrane fouling and inhibits voltage rise, making it a key pre-treatment step to ensure the long-term stable operation of the BMED unit.

[0127] Finally, it should be noted that the above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of this invention should be considered within the scope of protection of this invention.

Claims

1. A method for zero-discharge resource utilization of landfill leachate reverse osmosis concentrate, characterized in that, include: (1) Add coagulant to the concentrate for coagulation pretreatment, stir and then filter the supernatant to obtain the first effluent; (2) Obtain a bipolar membrane electrodialysis unit, wherein the bipolar membrane electrodialysis unit includes an anode chamber, an acid chamber, a salt chamber, an alkali chamber and a cathode chamber, a bipolar membrane is provided between the anode chamber and the acid chamber, an anion membrane is directly provided between the acid chamber and the salt chamber, a cation membrane is provided between the salt chamber and the alkali chamber, and another bipolar membrane is provided between the alkali chamber and the cathode chamber. The first effluent is passed through the salt chamber. Under the action of the electric field, the anions and cations in the first effluent pass through the anion membrane and the cation membrane respectively into the acid chamber and the alkali chamber, thereby achieving desalination to obtain the second effluent. (3) Adjust the pH of the second effluent to 2-3, and then introduce it into the UV-Fenton deep oxidation unit to excite Fe under ultraviolet light. 2+ The catalytic H2O2 generates hydroxyl radicals, which degrade the soluble and recalcitrant organic matter remaining in the second effluent to obtain the third effluent.

2. The method for zero-discharge resource utilization of landfill leachate reverse osmosis concentrate according to claim 1, characterized in that, The coagulant includes FeCl3, polyaluminum chloride, or Al2(SO4)3.

3. The method for zero-discharge resource utilization of landfill leachate reverse osmosis concentrate according to claim 2, characterized in that, The coagulant also includes polyacrylamide.

4. The method for zero-discharge resource utilization of landfill leachate reverse osmosis concentrate according to claim 3, characterized in that, The coagulant is FeCl3 and polyacrylamide.

5. The method for zero-discharge resource utilization of landfill leachate reverse osmosis concentrate according to claim 4, characterized in that, The dosage of FeCl3 is 1-3.5 g / L, and the dosage of PAM is 40-80 mg / L.

6. The method for zero-discharge resource utilization of landfill leachate reverse osmosis concentrate according to claim 1, characterized in that, Before introducing the first effluent into the salt chamber, adjust the pH of the first effluent to 9-10, and then add 0.1-0.3 mol / L of Na2CO3.

7. The method for zero-discharge resource utilization of landfill leachate reverse osmosis concentrate according to claim 1, characterized in that, The bipolar membrane electrodialysis unit operates at a voltage of 10-60V and a current density of 10-20mA / cm2.

8. The method for zero-discharge resource utilization of landfill leachate reverse osmosis concentrate according to claim 1, characterized in that, NaSO4 is placed in the anode chamber and cathode chamber, HCl is placed in the acid chamber, and NaOH is placed in the alkali chamber.

9. The method for zero-discharge resource utilization of landfill leachate reverse osmosis concentrate according to claim 1, characterized in that, In the UV-Fenton deep oxidation unit, H2O2 and Fe are added to the second effluent. 2+ At the same time, ultraviolet irradiation is carried out; The dosage of H2O2 is 5-8 g / L, Fe 2+ The dosage is 1-3 g / L, and the ultraviolet irradiation reaction time is 1-8 h.

10. The method for zero-discharge resource utilization of landfill leachate reverse osmosis concentrate according to claim 1, characterized in that, The acid and alkali produced by the bipolar membrane electrodialysis unit are recycled to the pH adjustment stage of the coagulation pretreatment unit.

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